The genetically engineered insect-resistant crops, Bt crops, were first commercially grown in 1996 and adopted in different countries. The economic benefits of Bt crops are reducing the use of insecticides and more safe to environment, however, development of resistance by insects might reduce their efficacy. Unfortunately, the field population evolved resistance to different Bt toxins and the number of resistant species is going to increase, which threat the continuous success of Bt crops. Thus, understanding the Bt resistance mechanisms, including the molecular basis of resistance is important for well-resistance control in Bt crops. This review paper displayed the mechanisms of insect pests resistance to Bt crops and appropriate strategies to delay and manage the resistance in Bt crops.